Buffer amplifier circuits are presently used in electronic equipment for isolating a driver circuit having a relatively high output impedance from a load, increasing the power level of a driving signal and establishing a desired quiescent direct current (DC) output potential. More specifically, integrated circuits often include buffer amplifier circuits which are electrically connected between the output terminals of differential amplifiers having differential-to-single ended converters and the loads for these amplifiers. Buffer amplifier circuits are sometimes required to provide a quiescent potential at the output terminal thereof which is substantially midway between power supply potentials to facilitate maximum excursion of a sinusoidal output signal, for instance. Such amplifiers are also required to maintain the balance of the driver differential amplifiers to prevent the creation of undesirable offset voltages within the differential amplifiers.
Some prior art buffer circuits rely on reference voltages for establishing the quiescent output voltage thereof. Unfortunately, such reference voltages often have a tendency to change in magnitude with temperature change or with power supplly magnitude variation. The resulting shift in quiescent potential can cause clipping of either the positive or negative extremes of the output signal thereby causing undesired distortion. Moreover, prior art circuits sometimes require a plurality of components that take up a large amount of area of an integrated circuit, which results in increased cost and decreased reliability as compared to circuits taking up less area. Moreover, some prior art circuits create an undesirable amount of voltage drop thereby decreasing the maximum possible amplitude of the output signal thereof. Furthermore, prior art circuits are sometimes difficult to test when provided in monolithic integrated circuit form because of the difficulty of predicting the dynamic and quiescent signal magnitudes therein.